A flow sensor is generally used for sensing a flow rate of a fluid (for example, gas or liquid) flowing through a fluid channel. Flow sensors are generally used in a wide range of applications, such as medical treatment, flight control, industrial processes, combustion control, weather monitoring, and many others. Due to different requirements from each of the applications, different types of flow sensors are needed for different applications. For instance, a flow sensor suitable for a breathing machine used in an intensive care unit (ICU) may be incapable of meeting requirements of a gas leakage detection system. A conventional flow meter, such as a hot wire anemometer, generally consumes much power. For a MEMS (Micro Electro Mechanical System) flow meter having a bypass channel, a pressure drop element, generally disposed between an inlet and an outlet of a bypass fluid channel within a main fluid channel, is typically employed to guide the fluid into the bypass fluid channel, thus causing a large pressure loss.
Therefore, it is necessary to provide a new flow sensor with improved pressure drop characteristics.